System and method for retrograde procedure

ABSTRACT

A system and method may be used for accessing an articular surface and for preparing an implant site on the articular surface. The method may include locating a portion of the articular. An access passage may be drilled towards the articular surface though bone behind the articular surface. An implant site may be excised in the articular surface relative to an axis defined by the access passage.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.11/326,133 (now U.S. Pat. No. 7,914,545), filed Jan. 5, 2006, whichclaims the Benefit of U.S. Provisional Patent Application Ser. No.60/641,552, filed Jan. 5, 2005. U.S. patent application Ser. No.11/326,133 (now U.S. Pat. No. 7,914,545), filed Jan. 5, 2006 is also acontinuation-in-part of U.S. patent application Ser. No. 11/209,170 (nowU.S. Pat. No. 7,901,408), filed Aug. 22, 2005, which claims the benefitof U.S. Provisional Patent Application Ser. No. 60/603,473, filed Aug.20, 2004. U.S. patent application Ser. No. 11/326,133 (now U.S. Pat. No.7,914,545), filed Jan. 5, 2006 is also a continuation in part of U.S.patent application Ser. No. 11/169,326, filed Jun. 28, 2005, whichclaims the benefit of U.S. Provisional Patent Application Ser. No.60/583,549, filed Jun. 28, 2004. U.S. patent application Ser. No.11/326,133 (now U.S. Pat. No. 7,914,545), filed Jan. 5, 2006 is also acontinuation in part of U.S. patent application Ser. No. 10/994,453 (nowU.S. Pat. No. 7,896,885), filed Nov. 22, 2004, which claims the benefitof U.S. Provisional Patent Application Ser. No. 60/523,810, filed Nov.20, 2003. Additionally, U.S. patent application Ser. No. 11/326,133 (nowU.S. Pat. No. 7,914,545), filed Jan. 5, 2006 is also a continuation inpart of U.S. patent application Ser. No. 10/308,718 (now U.S. Pat. No.7,163,541), filed Dec. 3, 2002. Then entire disclosures of all of theabove listed applications are incorporated herein by reference.

FIELD

The present disclosure is directed at a system and method for accessingan articular joint surface. The present disclosure is further directedat a method and system for replacing at least a portion of an articularsurface.

BACKGROUND

Articular cartilage, found at the ends of articulating bone in the body,is typically composed of hyaline cartilage, which has many uniqueproperties that allow it to function effectively as a smooth andlubricious load bearing surface. Hyaline cartilage problems,particularly in knee, hip joints, and should joints, are generallycaused by disease such as occurs with rheumatoid arthritis or wear andtear (osteoarthritis), or secondary to an injury, either acute (sudden),or recurrent and chronic (ongoing). Such cartilage disease ordeterioration can compromise the articular surface causing pain andeventually, loss of joint movement. As a result, various methods havebeen developed to treat and repair damaged or destroyed articularcartilage.

For smaller defects, traditional options for this type of probleminclude leaving the lesions or injury alone and living with it, orperforming a procedure called abrasion arthroplasty or abrasionchondralplasty. The principle behind this procedure is to attempt tostimulate natural healing. The bone surface is drilled using a highspeed rotary burr or shaving device and the surgeon removes about 1 mmof bone from the surface of the lesion. This creates an exposedsubchondral bone bed that will bleed and will initiate a fibrocartilagehealing response. One problem with this procedure is that the exposedbone is not as smooth as it originally was following the drilling andburring which tends to leave a series of ridges and valleys, affectingthe durability of the fibrocartilage response. Further, although thisprocedure can provide good short term results, (1-3 years),fibrocartilage is seldom able to support long-term weight bearing and isprone to wear, soften and deteriorate.

Another procedure, called Microfracture incorporates some of theprinciples of drilling, abrasion and chondralplasty. During theprocedure, the calcified cartilage layer of the chondral defect isremoved. Several pathways or “microfractures” are created to thesubchondral bleeding bone bed by impacting a metal pick or surgical awlat a minimum number of locations within the lesion. By establishingbleeding in the lesion and by creating a pathway to the subchondralbone, a fibrocartilage healing response is initiated, forming areplacement surface. Results for this technique may be expected to besimilar to abrasion chondralplasty. Another means used to treat damagedarticular cartilage is a cartilage transplant. Essentially, thisprocedure involves moving cartilage from an outside source or other kneeor from within the same knee into the defect. Typically, this is done bytransferring a peg of cartilage with underlying bone and fixing it inplace with a screw or pin or by a press fit. Although useful for smallerdefects, large defects present a problem, as this procedure requiresdonor pegs proportionate to the recipient bed. Large diameter lesionsmay exceed the capacity to borrow from within the same knee joint andrule out borrowing from another source.

Larger defects, however, generally require a more aggressiveintervention. Typically treatment requires replacing a portion or all ofthe articular surface with an implant or prosthetic having an outerlayer that that is polished or composed of a material that provides alubricious load bearing surface in approximation of an undamagedcartilage surface. Replacement of a portion, or all, of the articularsurface requires first cutting, boring, or reaming the damaged area toremove the damaged cartilage. A recess to receive an implant orprosthetic is formed at the damaged site. The implant or prosthetic isthen secured to the bone in an appropriate position in the recess.

The treatment and/or replacement procedure often requires direct accessto the damaged surface of the cartilage. While the most commonly damagedportions of some joints may easily be accessed for repair using aminimally invasive procedure some joints are not nearly as accessible.For example, the superior or medial femoral head, the medial humeralhead, the glenoid, etc. do not permit direct access sufficient to carryout replacement of the articular surface in a minimally invasive manner.In fact, repair of such obstructed joints often requires an invasiveprocedure and necessitates complete dislocation of the joint. Proceduresof such an invasive nature may be painful and require an extendedrecovery period.

Accordingly, it is an object of the present disclosure to provide amethod for replacing an articular joint surface that is obscured fromaxial approach that is less invasive than conventional procedures andmay not necessitate completely dislocating the joint.

BRIEF DESCRIPTION OF THE DRAWINGS

Features and advantages of the present invention are set forth bydescription of embodiments consistent therewith, which descriptionshould be considered in combination with the accompanying drawings,wherein:

FIG. 1 is a perspective view of an embodiment of a drill guideconsistent with the present disclosure;

FIG. 2 shows an embodiment of a modular aiming member consistent withthe present disclosure in perspective view;

FIG. 3 is a detailed view of an aiming tip of an aiming memberconsistent with the present disclosure;

FIG. 3 b is a detailed view of another embodiment of an aiming tipconsistent with the present disclosure;

FIG. 4 is a cross-sectional view of a drill guide consistent with thepresent disclosure in an application for providing retrograde access toan articular surface;

FIG. 5 illustrates an articular joint in cross-sectional view includinga retrograde access tunnel;

FIG. 6 illustrates a screw sheath inserted into a retrograde accesstunnel;

FIG. 7 shows an embodiment of an excision device consistent with thepresent disclosure in plan view;

FIG. 8 illustrates, in cross-sectional view, an embodiment of anexcision device consistent with the present disclosure;

FIG. 9 illustrates the excision device depicted in FIG. 8 with a cutterof the excision device in a deployed configuration;

FIG. 10 is an exploded view of an excision device consistent with thepresent disclosure;

FIG. 11 is a detailed exploded view of a distal end of an excisiondevice consistent with the present disclosure including a cutter;

FIG. 12 is cross-sectional view of a distal end of an excision deviceconsistent with the present disclosure;

FIG. 13 is a cross-sectional view of a handle region of an excisiondevice consistent with the present disclosure;

FIG. 14 is a perspective view of another embodiment of an excisiondevice consistent with the present disclosure;

FIG. 15 is a cross-sectional view of the excision device illustrated inFIG. 14 with the cutter in a retracted configuration;

FIG. 16 is a detailed cross-sectional view of the handle region of theexcision device depicted in FIG. 14 with the cutter in a retractedconfiguration;

FIG. 17 is a detailed cross-sectional view of the distal end of theexcision device of FIG. 14 with the cutter in a retracted configuration;

FIG. 18 depicts the excision device of FIG. 14 in cross-sectional viewwith the cutter in a deployed configuration;

FIG. 19 is a detailed cross-sectional view of the excision device ofFIG. 14 with the cutter in a deployed configuration;

FIG. 20 is a detailed cross-sectional view of the distal end of theexcision device of FIG. 14 with the cutter in a deployed configuration;

FIG. 21 is a detailed perspective view of the distal end of the excisiondevice shown in FIG. 14 with the cutter in an extended configuration;

FIG. 22 is a perspective view of a tibial articular surface including anembodiment of an articular surface implant consistent with the presentdisclosure;

FIG. 23 is a cross-sectional view of a tibia including an embodiment ofan articular surface implant consistent with the present disclosure;

FIG. 24 is an enlarged cross-sectional view of an embodiment of anarticular surface implant consistent with the present disclosure;

FIG. 25 is an exploded cross-sectional view of the articular surfaceimplant depicted in FIG. 24;

FIG. 26 is an exploded perspective view of the articular surface implantdepicted in FIG. 24;

FIG. 27 is an exploded top perspective view of the articular surfaceimplant depicted in FIG. 24;

FIG. 28 is a cross-sectional view of an articular surface implantconsistent with the present disclosure; and

FIG. 29 is a perspective view of a lower component of an articularsurface implant consistent with the present disclosure.

DESCRIPTION

By way of overview, the present disclosure provides a retrogradearticular surface replacement system that may include a method andapparatus for replacing at least a portion of an articular surface,including accessing a portion of the articular surface through a portionof bone. While the preceding overview and the following embodiments of asystem according to the present disclosure are directed at a system forreplacing at least a portion of an articular surface, the system hereinmay be used in connection with procedures other than the replacement ofportions of an articular surface. From a broad standpoint, the systemdisclosed herein may provide an apparatus and method for accessing abone, joint, etc., indirectly.

Referring to FIG. 1, an embodiment of a drill guide system 10 consistentwith the preset disclosure is shown. The drill guide system 10 maygenerally include an aiming member 12, a frame 14, and a cannulatedshaft 16. The aiming member 12 may be removably coupled to the frame 14at a first end 18 of the frame 14. Similarly, the cannulated shaft 16may be coupled to and/or may be releasably engaged to the frame 14 at asecond end 20 of the frame 14. The frame 14 may arrange the aimingassembly 12 and the cannulated shaft 16 in an angular and/or positionalrelationship to one another.

The aiming member 12 may generally include an aiming tip 22 disposed ata distal end of an arm 24. With additional reference to FIG. 2, theaiming member 12 may be a modular component that may be removablycoupled to the frame 14. According to an embodiment, the proximal end ofthe arm 24 may include a threaded portion 26 for removably coupling theaiming member 12 to the frame 14. The threaded portion 26 of the aimingmember 12 may be received through a cooperating opening in the first end18 of the frame 14. The aiming member 12 may be secured to the frame 14using a knob 28 that may be threadably engaged to the threaded portion26 of the aiming member 12. The aiming member 12 may include aprotrusion 30 that may be received in a cooperating cutout 32 in theframe 14. The protrusion 30 and cooperating cutout 32 may provide any ofa variety of functions. For example, the cooperating protrusion 30 andcutout 32 may orient the aiming tip 22 rotationally about the axis ofthe arm 24 relative to the frame 14. In this manner, the engagement ofthe protrusion 30 in the cooperating cutout 32 may maintain the aimingmember 12, and thereby the aiming tip 22, in a particular rotationalorientation relative to the frame 24. Additionally, the protrusion 30may aid in locating the aiming member 12 relative to the frame 14.Specifically, the extension of the aiming tip 22 from the frame 14 may,therefore, be fixed by the engagement of the protrusion 30 in the cutout32. With the protrusion 30 disposed in the cutout 32, the aiming member12 may be drawn toward the frame 14 by the threaded engagement betweenthe threaded portion of the aiming member 12 and the knob 28 until theprotrusion bottoms out in the cutout 32. In this manner, the aiming tip22 may be disposed a distance from the frame 14 based on the location ofthe cutout 32 and the distance between the protrusion 30 and the aimingtip 22.

Referring to FIG. 3, the aiming tip 22 is shown in detail. Asillustrated, the aiming tip 22 may have a slim profile, i.e., arelatively small thickness. The slim profile of the aiming tip 22 mayfacilitate positioning the aiming tip 22 within a joint while minimizingthe need to dislocate or separate the joint. The slim profile may,therefore, minimize the invasiveness and/or the ancillary damage causedby a procedure utilizing the drill guide 10.

As depicted in the illustrated embodiment, the aiming tip 22 of theaiming member 12 may include an opening 34 extending through the aimingtip 22. The opening 34 may allow the aiming tip 22 to be positionedproximate a defect in an articular surface and/or a proximate to adeterminable location on the articular surface. Positioning of theaiming tip 22 may be ascertained arthroscopically. Accordingly, it maybe possible to generally and/or precisely locate or center the aimingtip 22 about a location on an articular surface using a visual referenceon the articular surface.

The aiming tip 22 may have a projected geometry 38 that may correspondto the projected geometry of a load bearing surface of an articularsurface implant. Accordingly, the aiming tip 22 may be employed in themanner of a trial gauge to determine the size of an articular surfaceimplant necessary to replace a damaged or defective region of thearticular surface. The necessary size of an articular surface implantmay be determined by sequentially positioning a series of modular aimingfeatures 12 within the joint. Each of the series of aiming features 12may include an aiming tip 22 having different projected areas. In thismanner, a desired size of an articular surface implant may beascertained by visual inspection. As indicated above, visual inspectionmay be carried out arthroscopically.

Similarly, the aiming tip 22 of the aiming member 12 may be used as atrial gauge for at least generally measuring and/or determining thecontour of at least a portion of the articular surface. A set of aimingmembers 12 may be provided including aiming tips 22 each having acontacting surface 36 having a different geometry or contour. Aimingmembers 12 including aiming tips 22 with different geometry or contourcontacting surfaces 36 may be sequentially positioned on the articularsurface. The degree of fit between the contacting surface 36 of eachaiming tip 22 and the articular surface may be visually ascertainedand/or ascertained based at least in part on tactile feedback. Regardingthe latter, tactile feedback corresponding to the degree of fit betweenthe aiming tip 22 and the articular surface may, for example, be basedon the degree or amount of wobble of the aiming tip 22 when the aimingtip 22 is positioned on the articular surface. Alternative methods forascertaining the degree of fit between the aiming tip 22 and thearticular surface may also be employed. For example, various imagingtechniques, e.g. radioscopic imaging, may be used to determine the fitbetween the aiming tip 22 and the articular surface.

Consistent with the foregoing, the aiming tip 22 may be used in a mannersimilar to a feeler gauge, or trial gauge, to determine the size of animplant to replace a defect etc. in an articular surface and/or todetermine the geometry or contour of the articular surface in the regionof the articular surface to be replaced. An implant may be producedhaving a size and load bearing surface geometry that is based on, and/orthe compliment of, the size and/or geometry or contour of the articularsurface as determined using the modular aiming tips 22. Alternatively,an implant, having a desired size and load bearing surface geometry orcontour, based on the determined size and/or geometry or contour of theregion of the articular surface to be replaced, may be selected from aset of implants having a variety of sizes and/or surface geometries orcontours.

While the preceding implementation of the aiming tip 22 contemplatesdetermining both the size and the geometry or contour of a portion of anarticular surface to be replaced, the aiming tip 22 herein mayalternatively be employed to determine only one of the size and thegeometry of a portion of an articular surface to be replaced. Forexample, all of the modular aiming members 12 may be provided includingaiming tips having the same projected area or size, and differing onlyin the geometry or contour of the contacting surface 36. Furthermore,the aiming member 12 need not be used to accomplish any measuring orestimating processes. Rather, the aiming member 12 may by used only tolocate a desired region on the articular surface.

Another embodiment of an aiming tip 22 a is shown in FIG. 3 b. Similarto the above described embodiment, the aiming tip 22 a may include agenerally centrally located opening 34, and the aiming tip 22 a may havea projected area that may generally correspond to the projected geometryof a load bearing surface of an articular surface implant. The aimingtip 22 a may include a rim 33 and spokes 35 a-d that may define thecontact geometry of the aiming tip 22 a. That is, rather than having agenerally continuous surface, the contacting surface of the aiming tip22 a may include rim 33 and spokes 35 a-d. In the illustratedembodiment, the rim 33 may provide a circumferential contacting surfaceand the spokes 35 a-d may provide two generally orthogonal lines ofcontact. The rim 33 and spokes 35 a-d may together define the contactgeometry of the aiming tip 22 a.

In the illustrate embodiment four spokes 35 a-d are provided to definetwo generally orthogonal contact lines or geometry curves of the aimingtip 22 a. In other embodiments consistent with the present disclosure, agreater or fewer number of spokes may be used to define the contactgeometry of the aiming tip 22 a. Similarly, the spokes 35 a-d may bearranged to provide a relationship other than orthogonal. For example, amore complex contact geometry may be defined by five or more spokes.Furthermore, the aiming tip 22 a may be provided having a non-circularprojected area 38, including for example, oval and/or asymmetricalprojected areas.

As with the previous embodiment, the aiming tip 22 a may be used in themanner of a feeler gauge, or trial gauge, to determine the desired sizeand geometry of an implant to replace a portion of an articular surface.As described, the size of the implant may be ascertained based on theprojected area 38 of the aiming tip 22 a. The rim 33 and spokes 35 a-ddefining the contacting geometry of the aiming tip 22 a may be used toascertain the geometry of the articular surface based on the degree offit between the aiming tip 22 a and the articular surface. A pluralityof aiming tips 22 a having different projected areas 38 and/or contactgeometries, as defined by the rim 33 and spokes 35 a-d, may bepositioned on the articular surface in the region of the articularsurface to be replaced, and the size and fit between the aiming tip 22 aand the articular surface may be ascertained visually, tactilely, and/orusing various imaging techniques.

The open structure of the aiming tip 22 a, including a rim 33 and spoke35 a-d structure, may allow improved visibility during and afterpositioning of the aiming tip 22 a relative to the articular surface.The improved visibility may permit more controlled placement of theaiming tip 22 a on the articular surface. The improved visibility mayalso allow the fit between the aiming tip 22 a and the articular surfaceto be more easily ascertained. For example, it may be possible tovisually determine the fit between one or more of the spokes 35 a-dabout at least a portion of the length of the spoke. Additionally, theopen structure of the aiming tip 22 a may be lighter and more easilymanipulated. The open structure may also facilitate the passage oftools, fluids, etc. through the aiming tip 22 a. Various other featuresand advantages of the aiming tip 22 a will be readily appreciated bythose having skill in the art.

Turning to FIG. 4, an embodiment of the drill guide system 10 is shownin use. The aiming tip 22 is shown positioned within an articular jointand between two cooperating articular surfaces 40, 42. As describedabove, the aiming tip 22 may be positioned on one of the articularsurfaces 40 and generally centered around and/or locating a defect orother portion of the articular surface. With the aiming tip 22positioned in a location relative to the articular surface 40, the drillguide system 10 may be stabilized relative to the articular surface 40.As shown the cannulated shaft 16 may be advanced to contact a portion ofthe bone 44 at a location behind the articular surface 40. As bestillustrated in FIG. 1 the cannulated shaft 16 may include a serrateddistal end 46. The serrated distal end 46 of the cannulated 16 mayreduce and/or eliminate movement and/or sliding of the cannulated shaft16 on the bone 44. The engagement between the serrated distal end 46 andthe bone 44 may provide a more secure and/or stabile position of thedrill guide system 10 relative to the articular surface 40. The frame 14may include a locking feature 48, e.g. a cam, ratchet, frictional lock,etc. The locking feature 48 may maintain the cannulated shaft 16 inengagement with the bone 44.

Retrograde access to the articular surface 40 may be initiated byinserting a guide pin 50 through the bone 44 and toward the articularsurface. The guide pin 50 may be configured as a self-drilling pin. Forexample, the guide pin 50 may include drill features on at least aportion of the distal end of the guide pin 50. The lumen of thecannulated shaft 16 and the aiming member 12 may be maintained in apositional and/or angular relationship to one another by the frame 14.In one embodiment, the relationship of the cannulated shaft 16 and theaiming member 12 may be such that the lumen of the cannulated shaft 16intersects with the opening 34 defined in the aiming tip 22.Accordingly, the guide pin 50 may be positioned extending through thelumen of the cannulated shaft 16. The cannulated shaft 16 may stabilizethe guide pin 50 and maintain the guide pin 50 in a desired orientation.The guide pin 50, stabilized by the cannulated shaft 16, may be drilledinto the bone 44, for example by hand, or using a drive motor. The guidepin 50 may be drilled into the bone 44 until the distal end of the guidepin 50 penetrated the articular surface 40. According to one embodiment,penetration of the guide pin 50 through the articular surface 40 may beobserved through the opening 34 through the aiming tip 22 of the aimingmember 12. In one such embodiment, the guide pin 50 may intersect theopening 34 through the aiming tip 22. The guide pin 50 drilled into thebone 44 to the articular surface 40 in this manner may establish areference axis for subsequent procedures.

Once a reference axis through the bone 40 to the desired location on thearticular surface 40 has been established by the guide pin 50,retrograde access to the articular surface 40 may be established toenable subsequent retrograde procedures. After the guide pin 50 has beenpositioned extending through the bone 44, the drill guide system 10 maybe removed. The guide pin 50 may remain extending through the bone 44establishing the reference axis after the drill guide system has beenremoved.

Referring to FIG. 5, a retrograde access tunnel 52 may be created alongthe reference axis extending though the bone 44 and to the articularsurface 40. According to one embodiment, the access tunnel 52 may becreated using a cannulated drill, such as a cannulated twist drill. Thecannulated drill may be threaded over the guide pin 50, with the guidepin 50 supporting the cannulated drill and aligning the drill along thereference axis. The access tunnel 52 may then be drilled through thebone 44, operating the cannulated drill either manually or by using adrive motor. The cannulated drill may be carried by the guide pin 50extending through the lumen of the cannulated drill. The access tunnel52 may, accordingly, be created along the reference axis. The depth ofthe access tunnel 52 may be controlled by visual observation. Forexample, the articular surface 40 may be arthroscopically monitored.Drilling of the access tunnel 52 may be carried out until the cannulateddrill penetrates through the articular surface 40 by a generally desiredamount. Alternatively, the depth of the access tunnel 52 may becontrolled according to another methodology, for example, based onmarkings or features on the guide pin 50.

Turning to FIG. 6, after a retrograde access tunnel 52 has been createdextending through the bone 44 along the reference axis, a sheath 54 maybe at least partially inserted into the access tunnel 52. The sheath 54may reinforce the access tunnel 52 to prevent damage to the bone 44through which the access tunnel 52 is defined. The sheath 54 may alsoprovide a bushing or bearing surface for subsequent procedures, and/orthe sheath 54 may provide and/or ensure positive alignment with thereference axis.

In one embodiment, the sheath 54 may be provided as a screw sheath. Asshown in FIG. 6, a screw sheath 54 may be generally configured having atubular body 56 and a head 58. The tubular body 56 may be threaded on atleast a portion of the outside diameter thereof. The head 58 of thescrew sheath 54 may have an outside diameter greater than the outsidediameter of the tubular body 56 of the sheath 54. While the illustratedembodiment of the sheath is shown including a head having a largeroutside diameter than the body, this is not a necessary feature.Consistent with various alternative embodiments, the head may have anoutside diameter that is the same as, or smaller than, the outsidediameter of the body. According to still further embodiments, the sheathmay not include head. In such an embodiment, the tubular body may makeup the entire sheath, with at least a portion of the outside diameter ofthe tubular body being threaded.

The sheath 54 may be screwed into the access tunnel 52 in the bone 44.Screwing the sheath 54 into the access tunnel 52 may include at leastpartially threadably engaging the tubular body 56 of the sheath 54 withthe inside diameter of the access tunnel 52. The outside diameter of thesheath 54 and the depth of the threaded portion of the body 56 and theinside diameter of the access tunnel 52 may be selected to providedthreaded engagement between the sheath 54 and the access tunnel 52. Thecoordination of the diameters of the sheath 54 and the access tunnel 52may also be coordinated to minimize excessive and/or undesired damage tothe bone 44 when the sheath is screwed into the access tunnel 52.Additionally, the diameters of the sheath 54 and the access tunnel 52and the pitch, etc., of the threaded portion of the tubular body 56 maybe selected to facilitate and/or promote alignment of the sheath 54 withthe axis of the access tunnel 52 when the sheath 54 is screwed into theaccess tunnel 52. Initial alignment of the sheath 54 with the accesstunnel 52 may be facilitated by providing the distal end of the sheath,and/or the outer opening of the access tunnel 52, having a chamfer ortaper.

The sheath 54 may be screwed into the access tunnel 52 by rotationallydriving the sheath 54 in order to engage the threaded portion of thetubular body 56 with the access tunnel 52 and to threadably advance thesheath 54 into the access tunnel 52. As shown, the head 58 of the sheath54 may include a socket 60 defined therein. According to one embodiment,the socket 60 may be a hex, spline, etc. socket. The sheath 54 may bedriven into the access tunnel 52 using a driver 62 including drive head64 that is shaped to be received in the socket 62 in a torsionally rigidmanner, thereby allowing torque to be transmitted from the driver 62 tothe sheath 54.

The driver 64 may include a shaft 66 sized to extend through the tubularbody 56 of the sheath 54. The shaft 66 may be provided as an extensionof the drive head 64, or may be a separate component extending throughthe drive head 64 and into the tubular body 56 of the sheath 54. Theshaft 66 may be employed to position a distal end of the sheath 54 inthe bone 44 at a depth below the articular surface 40. Depth positioningof the sheath 54 relative to the articular surface 40 may beaccomplished by providing the shaft 66 having a known length relative tothe length of the sheath 54. According to one embodiment, a shoulder maybe defined by the bottom of the socket 60 and the cannula through thetubular body 56 of the sheath 54. The shoulder may allow the drive head64 to positively seat in the socket 60. Accordingly, when the drive head64 is seated in the socket 60 the extension of the shaft 66 beyond thedistal end of the sheath 54 may be ascertained by direct measurementand/or by calculation based on the respective length of the shaft 66 andof the sheath 54.

In another embodiment, the drive head 64 of the driver 62 may include ashoulder having a larger diameter than the socket 60. Accordingly, whenthe drive head 64 is engaged in the socket 60 the shoulder of the drivehead 64 may bear against the head 58 of the sheath 54. Accordingly, theprojection of the shaft 66 beyond the distal end of the sheath may bethe difference between the length of the shaft 66 from the shoulder ofthe drive head 64 and the length of the sheath 54. Of course, theprojection of the shaft 66 beyond the distal end of the sheath 54 mayalso be directly measured. This embodiment may be used alone, incombination with the preceding embodiment, and/or in combination withany of various other arrangements that may be used to provide arepeatable and/or relatively stable extension of the shaft 66 beyond thedistal end of the sheath 54.

According to any of the preceding embodiments, the distal end of thesheath 54 may be positioned at a depth below the articular surface 40 bydriving the sheath 54 into the access tunnel 52, and thereby threadablyadvancing the sheath 54 within the access tunnel 52, until the distalend 68 of the shaft 66 reaches a predetermined height relative to thearticular surface 40. According to an embodiment consistent with thepresent disclosure, the projection of the shaft 66 beyond the distal endof the sheath 54 may be equal to the desired final depth of the distalend of the sheath below the articular surface 40. Accordingly, thesheath 54 may be threadably driven into the access tunnel 52 until thedistal end 68 of the shaft 66 is tangent, or flush, with the articularsurface 40. According to various other embodiments, the relativeextension of the shaft 66 beyond the distal end of the sheath 54 may besuch that the distal end of the sheath 54 is at the desired depth belowthe articular surface 40 when the distal end 68 of the shaft 66 iseither recessed below the articular surface 40 or when the distal end 68of the shaft 66 protrudes above the articular surface 40. The necessaryamount of recess below, or protrusion above, the articular surface 40may be ascertained by measuring or by reference to indicia on the shaft66, etc.

According to one embodiment, the sheath 54, positioned within the accesstunnel 52 with the distal end of the sheath 54 located a predetermineddistance below the articular surface 40, may be used to support anexcision device 70 to enable at least a portion of the articular surface40 to be excised. Turning to FIG. 7, an embodiment of an excision device70 that may be used for excising at least a portion of the articularsurface 40 is shown. Generally, the excision device 70 may include adrive shaft 72 that is sized to be received through the tubular body 56of the sheath 54. In one embodiment, the excision device 70 may alsoinclude a cutter 74 adjacent the distal end of the shaft 72 and a handle76 disposed adjacent the proximal end of the shaft 72.

Referring to FIG. 8, the distal end of the excision device 70 is shownreceived through the sheath 54. As depicted, the cutter 74 may be placedin one position, for example, such that the cutter 74 is configured tobe at least partially retracted to allow the distal end of the shaft tobe inserted into and/or through the sheath 54. While the cutter 74 isshown retracted entirely within the diameter of the shaft 72, otherembodiments are contemplated by this disclosure. Consistent with theillustrated embodiment, the outside diameter of the shaft 72 of theexcision device 70 may be sized to be rotatably and/or slidable receivedwithin the inside diameter of the sheath 54. According to oneembodiment, the tolerance between the outside diameter of the shaft 72of the excision device 70 and the inside diameter of the sheath 54 maybe such that, while the shaft may be rotatably and/or slidably disposedwithin the sheath 54, the shaft 72 of the excision device 70 may bemaintained generally aligned with the axis of the sheath 54.

Turning next to FIG. 9, the cutter 74 may be moved to another position,for example a deployed configuration, in which the cutter 74 extendsoutwardly from the shaft 72. Excision of the articular surface 40 and/orexcision of the underlying bone 44 may be achieved by rotating theexcision device 70 during and/or after deployment of the cutter 74.According to one embodiment, the excision device 70 may be positioned sothat at least a portion of the cutter 74 is disposed below the articularsurface 40. The cutter 74, and the shaft 72 therewith, may be rotated asthe cutter 74 is deployed, thereby excising an implant site 78 in thearticular surface 40 and/or the underlying bone 44. The cutter 74 may beconfigured to be gradually and/or incrementally moved to the deployedconfiguration. Accordingly, the articular surface 40 and/or bone 44 maybe gradually excised. While not necessary, gradual excision may, in somesituations, decrease the occurrence of irregular and/or undesiredchipping, cracking, fragmenting, etc., of the bone 44 and/or of thearticular surface 40.

According to another embodiment, the excision device 70 may be advancedinto the joint so that at least a portion of the cutter 74 is disposedabove the articular surface 40. The cutter 74 may then be at leastpartially deployed, with at least a portion of the cutter 74 beingdeployed above the articular surface 40. The cutter 74, and the shaft 72therewith, may be rotated before, during, and/or after the at leastpartial deployment of the cutter 74. As the cutter 74 and shaft 72 arerotated the excision device 70 may be withdrawn, thereby urging thecutter 74 into the articular surface 40. Various other methodologies myalso be employed to excise an implant site 78 in the articular surface40 and/or in the underlying bone 44 using an excision device 70according to the present disclosure.

Consistent with the illustrated embodiment, the configuration of thedistal tip of the excision device 70 and the mode of deployment of thecutter 74 may be such that collateral damage to adjacent bone and/orarticular cartilage, for example of an adjacent cooperating articularsurface e.g. 42 in FIG. 5, may be reduced and/or prevented.Additionally, as most clearly observed in FIG. 11, the cutter 74 mayinclude a shelf 75 that may contact and/or bear against a distal end ofthe sheath 54 as cutter 74 is withdrawn towards the sheath 54 during theexcision of the articular surface 40 and underlying bone 44. Theinteraction of the shelf 75 and the distal end of the sheath 54 may,with the distal end of the sheath 54 located a predetermined distancebelow the articular surface 40, control the depth of the implant site 78created by excising the articular surface 40 and the underlying bone 44.The shelf 75 of the cutter 74 may have a flat, relieved, and/or roundedprofile to reduce and/or eliminate grinding, shaving, or otherwisefreeing fragments of the sheath 54 when the cutter 74 contacts thedistal end of the sheath 54.

Referring to FIG. 10, an exploded diagram of an embodiment of anexcision device 70 consistent with the present disclosure is shown. Inaddition to the shaft 72, the cutter 74, and the handle 76, the excisiondevice 70 may also include a pushrod 80 extending generally between thecutter 74 and the handle 76. One or more bearings 82, 84 may beassociated with the handle 76 to provide a hub assembly 86. The shaft 72of the excision device 70 may be rotatably received at least partiallywithin the hub assembly 86 provided by the handle 76 and bearings 82,84. The shaft 72 may further include one or more longitudinal slots 88,90 in the general region of the hub assembly 86. The longitudinal slots88, 90 may allow the pushrod 80 to be axially translated within theshaft 72. The distal end of the excision device 70 may include a cuttertip 92 that may carry the cutter 74.

Turning next to FIG. 11, the distal end of the excision device 70 isshown in a detailed exploded view. As illustrated, the distal end of theshaft 72 may include a cutter deployment window 94 though which thecutter 74 may extend or project when the cutter 74 is in a deployedconfiguration. The cutter tip 92 may be sized to be at least partiallyreceived inside the cannulated shaft 72. The cutter tip 92 may beretained in the shaft 72 using any suitable means or configuration,including friction fit, adhesive bonding, welding, staking, etc.

Consistent with the illustrated embodiment, the excision device 70 mayemploy a system of arcs-in-grooves to enable the cutter 74 to movebetween a stowed, or retracted, configuration and a deployed, orextended, configuration. The arcs-in-grooves arrangement may create avirtual pivot about which the cutter 74 may pivot or rotate between thestowed configuration and the deployed configuration. Consistent with thepresent disclosure, the virtual pivot is a point or an axis about whichthe cutter 74 may rotate. However, the cutter 74 is not physicallyconnected to the virtual pivot, e.g., as by an axle or pivot pin. Assuch, the cutter 74 may be capable of being engaged to the drive shaft72, for example, through the system of arcs-in-grooves.

The arcs-in-grooves arrangement utilized herein may provide relativesimplicity from the stand-point of mechanical operation and assembly.Additionally, the arcs-in-grooves arrangement may provide a moment armbetween the cutter 74 and the virtual pivot point that is greater thanthe moment arm that may be achieved by rotating the cutter 74 around anactual physical pivot, such as a pin, within the same package size,i.e., within the diameter of the shaft 72. The longer moment armachievable using a virtual pivot in an arcs-in-grooves arrangement mayallow the cutter 74 to achieve a relatively higher deployment torque fora given actuation force.

The cutter tip 92 may include a primary arcuate groove 96 and asecondary arcuate groove 98. As shown, the primary and secondary grooves96, 98 may be provided as concave surfaces extending into the cutter tip92. The primary and the secondary arcuate grooves 96, 98 may beconcentric with one another. Additionally, each of the primary and thesecondary arcuate groove 96, 98 may have a constant radius. Consistentwith the illustrated embodiment, while the primary and secondary arcuategrooves 96, 98 may be concentric and may each have a constant radius,the radius of one of the arcuate grooves, e.g. the primary arcuategroove, may be greater than the radius of the other arcuate groove,e.g., the secondary arcuate groove 98.

The cutter 74 may include a primary arcuate bearing surface 100 and asecondary arcuate bearing surface 102. Similar to the primary and thesecond arcuate grooves 96, 98, the primary and secondary arcuate bearingsurfaces 100, 102 may each have a constant radius and may be concentricwith one another. Additionally, in one embodiment the primary andsecondary arcuate bearing surfaces 100, 102 of the cutter 74 may beprovided as the compliment of the primary and the secondary arcuategrooves 96, 98. That is, the primary and secondary arcuate bearingsurfaces 100, 102 may cooperate with the primary and the secondaryarcuate grooves 96, 98 to allow arcuate sliding movement of the cutter74 about the center of the primary and the secondary arcuate grooves 96,98. The foregoing interaction between the primary and secondary arcuategrooves 96, 98 and the primary and secondary arcuate bearing surfaces100, 102 does not require that the radii of the primary and secondaryarcuate bearing surfaces 100, 102 be the same as the respective radii ofthe primary and the secondary arcuate grooves 96, 98.

According to a related embodiment, the cutter may include an arcuateprotrusion in addition to and/or instead of the primary and secondaryarcuate bearing surfaces. The arcuate protrusion or rib may be receivedin a channel in the tip, the channel having an arcuate cooperatingfeature corresponding to the arcuate protrusion. According to such anarrangement, cutter may rotate about a virtual pivot as discussed above.The interaction of the protrusion and the channel may restrict and/orlimit non-rotational movement of the cutter, e.g. wobbling, twisting, ortranslation of the cutter along the pivot axis. The protrusion andchannel configuration may therefore, in some embodiments, furtherstabilize the cutter. In a similar embodiment, the cutter tip may beprovided having an arcuate protrusion that may be received in a channelin the cutter. The operation of such an embodiment may be as generallydescribed.

With additional reference to FIG. 12, in the illustrated excision device70, actuation of the cutter 74 may be achieved using the pushrod 80slidably disposed within the shaft 72, which may, in some embodiments bea cannulated shaft. The cutter 74 may include a boss 104 that may be atleast partially received within a slot 106 of the pushrod 80.Translating the pushrod 80 axially toward the distal end of the excisiondevice 70 may urge the cutter 74 toward the distal end of the excisiondevice 70. Cooperation of the primary and secondary arcuate bearingsurfaces 100, 102 against the respective primary and secondary arcuategrooves 96, 98 may cause the cutter 74 to rotate within the primary andsecondary arcuate grooves 96, 98 about the center of the primary andsecondary arcuate grooves 96, 98. Rotation of the cutter 74 about thecenter of the primary and secondary arcuate grooves 96, 98 may cause thecutter 74 to deploy through the deployment window 94 and extendoutwardly from the shaft 72.

Similarly, when the cutter 74 is in a deployed configuration, the cutter74 may be retracted to a stowed configuration by axially translating thepushrod 80 toward the proximal end of the excision device 70. When thepushrod 80 is axially translated toward the proximal end of the excisiondevice 70, the proximal edge of the slot 106 in the pushrod 80 may bearagainst the boss 104 of the cutter 74. The force of the slot 106 on theboss 104 may urge the primary and secondary arcuate bearing surfaces100, 102 toward the proximal portion of the primary and secondaryarcuate grooves 96, 98. The force of the primary and second arcuatebearing surfaces 100, 102 against the primary and secondary arcuategrooves 96, 98 may cause the cutter 74 to rotate about the center of theprimary and secondary arcuate grooves 96, 98. Rotation of the cutter 74about the center of the primary and secondary arcuate grooves 96, 98 maycause the cutter 74 to rotate in through the deployment window 94 toachieve a stowed configuration at least partially within the shaft 72.

FIG. 13 illustrates an embodiment of the hub assembly 86 in detailedcross-sectional view. Generally, the hub assembly 86 may allow thehandle 76 to be maintained rotationally stable or unmoving while theshaft 72, the pushrod 80, and the cutter 74 therewith, may be rotated toexcise the articular surface 40 and underlying bone 44. Additionally,the hub assembly 86 may allow the pushrod 80 to be axially translatedwithin the shaft 72 while the shaft 72, along with the pushrod 80,rotate.

Consistent with the illustrated embodiment, the handle 76 may be coupledto the shaft 72 by one or more bearings 82, 84. The bearings 82, 84 mayallow the shaft 72 to rotate independently of the handle 76. In additionto allowing the shaft 72 to rotate independently of the handle 76, thebearings 82, 84 may also allow the handle 76 to slide axially along theshaft 72. Axial movement of the handle 76 along the shaft 72 may beachieved as a function of the design and/or construction of the bearings82, 84. For example, the bearings 82, 84 may facilitate axial as well asrotational movement, e.g., as may be achieved with ball bearings.According to another embodiment, axial movement of the handle 76relative to the shaft 72 may be a function of the fit between thebearings 82, 84 and the shaft 72. For example, a loose fit between thebearings 82, 84 and the shaft 72 may allow sliding movement of thehandle 76 along the shaft 72. Consistent with the present disclosure,the bearings 82, 84 herein may be provided as ball bearing and/or rollerbearings. Alternatively, the bearings 82, 84 may be provided as bushingsformed from a low friction material, such as bronze, Teflon™,polyethylene, ultra-high molecular weight polyethylene, etc. Othersuitable materials, designs, and/or configurations of the bearings mayalso be employed consistent with the present disclosure.

Actuation of the pushrod 80 within the shaft 72 while the shaft 72 isrotating may be accomplished by sliding the handle 76 along the shaft72. In the region of the hub assembly 86 the shaft 72 may include one ormore axial slots 88, 90, as best observed in FIG. 10. The pushrod 80 mayinclude at least one radially extending hole 108, 110 corresponding toeach slot 88, 90. A pin 112, 114 may be provided extending through eachhole 108, 110 in the pushrod 80 and at least partially extending fromthe respective slot 88, 90 in the shaft 72. Each pin 112, 114 may coupleeach bearing 82, 84 to the pushrod 80 through the slots 88, 90.Accordingly, axial movement of the bearings 82, 84 along the shaft 72may move the pins 112, 114 in the slots 88, 90, thereby producing axialmovement of pushrod 80.

Consistent with the foregoing illustrated and described excision device70, axial movement of the bearings 82, 84 along the shaft 72 may axiallytranslate the pushrod 80 within the shaft 72. Accordingly, when theshaft 72 is rotated the pushrod 80 and at least a portion of eachbearing 82, 84 may rotate with the shaft 72, while the handle 76 may bemaintained rotationally stationary. Axial movement of the handle 76along the shaft 72 may cause axial movement of the bearings 82, 84 alongthe shaft 72. The axial movement of the bearings 82, 84 along the shaft72 may cause axial translation of the pushrod 80 within the shaft 72.The axial translation of the pushrod 80 may actuate the cutter 74,moving the cutter 74 between a stowed configuration and a deployedconfiguration. Accordingly, the shaft 72, pushrod 80, and cutter 74 maybe rotated, e.g., by a drive motor, while the excision device 70 may bestabilized by the handle 76, which may also deploy and retract thecutter 74.

Referring to FIGS. 14 through 21, another embodiment of an excisiondevice 200 consistent with the present disclosure is shown. Theillustrated excision device 200 may generally include a shaft 202 havinga handle 204 disposed adjacent to a proximal region of the shaft 202.The excision device 200 may further include a cutter 206 that isdeployable from a distal region of the shaft 202, as illustrated.

As shown in cross-sectional view in FIG. 15, the shaft 202 of theexcision device 200 may be a cannulated shaft. A pushrod 208 may bedisposed within the lumen of the cannulated shaft 202. The pushrod 208may be coupled to the handle 204 at a proximal end, and may be coupledto the cutter 206 at a distal end. The pushrod 208 may be eitherdirectly or indirectly coupled to the handle 204 and/or to the cutter206. When the cutter 206 is in a retracted configuration, as shown inFIG. 15, the cutter 206 may be disposed at least partially and/orcompletely within the lumen of the cannulated shaft 202.

With reference to FIG. 16, the handle 204 may be slidably and rotatablydisposed on the shaft 202. The handle 204 may be coupled to the shaft202 by two bearings 210, 212. In other embodiments consistent with thepresent disclosure, a single bearing may suitably be employed forcoupling the handle 204 to the shaft 202. The bearings 210, 212 may beball bearings, roller bearings, bushings, etc. As shown the bearings210, 212 may be coupled to the pushrod 208 disposed within the lumen ofthe shaft 202 by pins 214, 216 extending through the pushrod 208 and apair of opposed slots 218, 220 in the shaft 202. The pins 214, 216 maybe received in the bearings 210, 212, thereby coupling the bearings 210,212 and the pushrod 208.

Consistent with the illustrated embodiment, the shaft 202, pushrod 208and at least a portion of each bearing 210, 212 may rotate relative tothe handle 204. Furthermore, the bearings 210, 212 and the pushrod 208may be in a generally fixed axial relationship with the handle 204. Thehandle 204, pushrod 208, and bearings 210, 212 may be slidable disposedon the shaft 202, with the bearings 210, 212 coupled to the pushrod 208by the pins 214, 216 axially slidably disposed through the slots 218,220 in the shaft 202.

In one embodiment, the handle 204 may be releasably retained in aproximal position relative to the shaft 202. In the illustratedembodiment, the handle 204 may be releasably retained in a proximalposition on the shaft 202 by a ring 222. When the handle 204 is in aproximal position the ring 222 may be at least partially received in arecess 224 in the handle and a recess 226 in the shaft 202. Accordinglythe handle 204 may be releasably retained in position on the shaft 202.In one embodiment, at least a portion of the ring 222 may be resilientlyradially deflectable. The handle 204 may be released from engagementwith the ring 222 by applying a distally directed axial force on thehandle 204. The distally directed axial force may cause the ring tocompress or deflect radially inwardly from the recess 224 in the handle204 and allow the handle 204 to move axially from the ring 222. In oneembodiment, the handle 204 may be releasably engaged with the ring 222by applying a proximally directed force on the handle 204, causing thering 222 to compress or deflect radially inwardly and allowing therecess 224 to move into position and engage the ring 222. As describedabove, the handle 204 may be in a generally fixed axial relationshiprelative to the pushrod 208. Accordingly, when the handle 204 isreleasably retained in a proximal position on the shaft 202, the pushrod208 may also be releasably retained in a proximal position relative tothe shaft 202.

As shown in FIG. 17, when the handle 204 is in a proximal position, asdepicted in FIG. 16, the cutter 206 may be in a retracted or stowedconfiguration. When the cutter 206 is in a retracted configuration thecutter 206 may be at least partially and/or completely disposed withinthe lumen of the shaft 208.

The cutter 206 may be pivotally coupled to the pushrod 208 by a pivotpin 228. The pivotal coupling between the cutter 206 and the pushrod 208may allow the cutter 206 to pivot about an axis generally perpendicularto the axis of the shaft 202. As indicated by the arrows in FIG. 17,moving the cutter 206 distally may urge the cutter 206 against thedistal tip 230 of the excision device 200. A portion of the distal tip230 may include an angled or arcuate surface 232 that may pivot thecutter 206 outwardly when the cutter 206 is urged against the surface232. A blade portion 234 of the cutter 206 may deploy through a firstdistal slot 236 in the shaft 202. According to one embodiment, a tabportion 238 of the cutter 206 may be at least partially received inand/or through a second distal slot 240 in the shaft 202.

With specific reference to FIGS. 18 and 19, the excision device 200 isillustrated with the handle 204 in a distal position. As shown, when thehandle 204 is in a distal position, the pushrod 208 is also in a distalposition, and the cutter 206 may be in a deployed configuration,extending at least partially from the shaft 202. The handle 204 may bereleased from the ring 222 in a distal position, thereby allowingsliding and rotational movement of the handle 204 with respect to theshaft 202.

As shown in FIG. 19, when the handle 204 is in a distal position, thepins 214 and 216 may be in a distal position within the slots 218, 220in the shaft 202. Additionally, in a distal position the handle 204 maycontact a resilient feature 242. The resilient feature 242 may beresiliently deflectable or deformable along the axis of the shaft 202.Accordingly, when the handle 204 is move distally against the resilientfeature 242, the resilient feature 242 may deflect or deform to permitdistal movement of the handle 204, while applying a proximally directedspring force against the handle 204. Consistent with an embodimentherein the resilient feature 242 may be a spring, such as a short coilspring or a wave spring. As used herein, a wave spring may generallyresemble a washer having an undulating configuration that is resilientlydeflectable. Various other springs and resilient features, e.g.,elastically deformable features, may be used herein.

The handle 204 may be urged distally against the spring force of theresilient feature 242 and the handle may engage locking feature 244. Thelocking feature 244 may engage the handle 204 to maintain the handle 204in a distal position. According to one embodiment, the locking feature244 may be a twist-lock feature. In such an embodiment, the handle 204may be moved distally to engage the locking feature 244 and then thehandle may be rotated about the shaft 202 relative to the lockingfeature 244 thereby releasably engaging the locking feature 244. In onespecific embodiment, the locking feature 244 may be partially receivedin a distal end of the handle 204. When the handle 204 is rotatedrelative to the locking feature 244 cooperating features, such asprotrusions and indentations, on the handle 204 and locking feature 244may engage one another to releasably retain the handle 204 in a distalposition.

According to an embodiment herein, the proximally directed spring forceapplied to the handle 204 by the resilient feature 242 may aid inlocking the handle 204 in a distal position with the locking feature244. As discussed above, the resilient feature 242 may urge the handle204 proximally. Once the handle 204 has been engaged with the lockingfeature 244, the proximal force on the handle 204 may maintain thehandle 204 in locking engagement with the locking feature 244.

A detailed view of a cutter 206 according to the illustrated embodimentis shown in a deployed configuration in FIG. 20. As previouslymentioned, the cutter 206 may be moved from a retracted or stowedconfiguration to a deployed configuration when the cutter 206 is moveddistally by distal translation of the pushrod 208 within the shaft 202.The blade portion 234 of the cutter 206 may contact the surface 232 ofthe distal tip 230 of the excision device 200. The angled or arcuategeometry of the surface 232 and/or of the blade portion 234 may causethe cutter 206 to pivot outwardly through the slot 236 in the shaft 202about a pivot axis 228.

As illustrated, when the cutter 206 is in a deployed configuration astraight tang portion 246 of the cutter 206 may contact a straight wallportion of the distal tip 230, which may extend generally transverse tothe axis of the shaft 202. Additionally, when the cutter 206 is in adeployed configuration, a distal end 250 of the pushrod 208 may bearagainst a generally flat region of the spine 252 of the cutter 206. Inthis manner, the cutter 206 may be secured between the distal tip 230and the pushrod 208 in a deployed configuration.

With additional reference to FIG. 21, when the cutter 206 is in adeployed configuration, the cutter 206 may resist wobbling and/ortorsional loading. As depicted, the width of the cutter 206 may beclosely toleranced to the width of the slot 236. That is, the width ofthe cutter 206 may be such that the sides 254 of the cutter 206 may bein contact with, or closely spaced from, the side of the slot 236.Accordingly, a side loading of the cutter 206 may be transmitted to theshaft 202 as a torsional force, without substantial deflection ormovement of the cutter 206. Similarly, the tab 238 of the cutter 206 maybe closely toleranced to the width of the slot 240 in the shaft 202.Supporting the cutter 206 on each side of the shaft 202 may allow thecutter 206 to resist side loading and/or wobbling around the axis of theshaft 202.

An excision device 200 consistent with the depicted embodiment of FIGS.14-21 may be employed for excising at least a portion of an articularsurface and/or at least a portion of underlying bone in a manner similarto the excision device previously described with reference to FIGS. 8and 9. Specifically, the excision device 200 may be inserted extendingat least partially through the sheath 54. According to one embodiment,extension of the excision device 200 through the sheath 54 may becontrolled by observing the position of the distal tip 230 of theexcision device 200 relative to the articular surface 40 to be excised.Observation of the position of the distal tip 230 relative to thearticular surface 40 may be accomplished arthroscopically or using anysuitable imaging or referencing systems.

When the excision device 200 has been positioned extending at leastpartially through the sheath 54 the shaft 202, and the cutter 206 andpushrod 208, may be rotationally driven within the sheath 54. Accordingto one embodiment, the shaft 202, cutter 206, and pushrod 208 may berotationally driven by a drive motor, such as a drill. The excisiondevice 200 may be stabilized at the proximal end thereof by the handle204, which may be maintained rotationally independent from the shaft 202by the bearings 214, 216. The cutter 206 may be deployed from the shaft202 by moving the handle 204 to a distal position, thereby also movingthe pushrod 208 to a distal position. Movement of the pushrod 208 to adistal position may cause the cutter 206 to be deployed from the shaft202 in the previously described manner. Once the cutter 206 has beenfully deployed by moving the handle 204 to a distal position, the cutter206 may be maintained in the deployed configuration by engaging thehandle 204 with the locking feature 244.

Rotation of the shaft 202 with the cutter 206 in a deployedconfiguration may excise at least a portion of the articular surface 40and/or the underlying bone 44. As the articular surface 40 and/orunderlying bone 44 are being excised by the cutter 206, the excisiondevice may be moved distally toward the sheath 54 until the cutter 206contacts the distal end of the sheath 54. The cutter may include a shelf256 on the proximal side, or spine, of the cutter 206. The shelf 256 maycontact the distal end of the sheath 54, thereby preventing furtherwithdrawal of the excision device 200. As discussed previously, sheath54 may be positioned at a depth from the articular surface 40 to definea depth of an implant site created by excising at least a portion of thearticular surface 40 and/or at least a portion of the underlying bone.The shelf 256 and/or the distal end of the sheath 54 may be formed toprevent and/or minimize the production of debris resulting fromrotational contact between the cutter 206 and the sheath 54.

Referring to FIG. 22, an articular surface 40 is illustrated in which aportion of the articular surface 40 includes an articular surfaceimplant 300 consistent with the present disclosure. According to oneembodiment, the implant 300 may be installed in an implant site 78, suchas may be formed using a retrograde access system as describedpreviously. The implant 300 may have a load bearing surface 302 that mayreplace at least a portion of the excised articular surface 40 of thebone 44. According to one embodiment, the load bearing surface 302 ofthe implant 300 may have a geometry that is based on the geometry orcontour of the portion of the articular surface 40 being replaced. Asused in any embodiment herein, a geometry of the load bearing surfacebased on the geometry of the articular surface 40 being replaced maymean that the geometry of the load bearing surface 302 may providesimilar mechanical action in relation to a cooperating articularsurface, soft tissue, etc during articulation of the joint.

Consistent with one embodiment herein, the geometry or curvature of theload bearing surface 302 of the implant 300 may be provided based onquantitative and/or qualitative reference to none, any, all, or anycombination of the portion of the articular surface being replaced bythe implant 300, the articular surface 40 receiving the implant, thegeometry of a cooperating implant, and/or the geometry of a cooperatingarticular surface. As discussed previously, the geometry or contour ofthe portion of the articular surface 40 being replaced may bequalitatively and/or quantitatively determined using aiming tip 22 ofthe drill guide system 10. Various other methods for determining thegeometry of the portion of the articular surface 40 being replaced mayalso be employed, including visual approximation.

With general reference to FIGS. 23 through 28, according to oneembodiment an articular surface implant 300 consistent with the presentdisclosure may be provided as an assembly including an upper component304 and a lower component 306. The upper component 304 may include theload bearing surface 302. The lower component 306 may be configured tobe disposed within the implant site 78 and may be capable of seatingagainst the bottom surface 79 of the implant site 78.

The lower component 306 may define a recess 308 capable of receiving atleast a portion of the upper component 304. The lower component 306 mayinclude a shelf feature 310 about at least a portion of the bottomregion of the recess 308. The shelf feature 310 may be capable ofsupporting at least a portion of the bottom surface 312 of the uppercomponent 304. Stresses and loads applied to the load bearing surface302 of the upper component may be transferred through the bottom surface312 of the upper component to the lower component at the shelf feature310. Stresses and loads transferred to the lower component 306 at theshelf feature may be transferred to the bone 44 containing the implant300 through the base 314 and/or sides 316 of the lower component 306.

The upper component 304 may additionally include a locking feature 318extending from the bottom surface 312. The locking feature 318 may becapable of being coupled to the lower component 306 of the implant 300.As depicted, for example in FIGS. 26 and 27, the locking feature 318 mayhave an elongated shape. The lower component 306 may include acorresponding locking recess 320 capable of receiving the lockingfeature 318. The elongated geometry of the locking feature 318 and thelocking recess 320 may facilitate aligning the upper component 304 withthe lower component 306 and/or may reduce and/or prevent rotation of theupper component 304 relative to the lower component.

As best depicted in FIG. 24, coupling of the upper component 304 and thelower component 306 may be at least in part achieved using cooperatingprotrusions 322 on the locking feature 318 of the upper component 304and indentations, or undercuts, 324 on the lower component 306.Consistent with such an arrangement, the locking feature 318 of theupper component 304 may be pressed into the locking recess 320 of thelower component 320 resiliently deforming the locking feature 318 and orthe locking recess 320 until the protrusions 322 of the locking feature318 align with the indentations, or undercuts, 324 in the locking recess320. When the protrusions 322 and indentations, or undercuts, 324 alignwith one another, the locking feature 218 and or the locking recess 320may resiliently recover to provide locking engagement between the uppercomponent 304 and the lower component 306. Various other cooperatingfeatures may additionally, or alternatively be employed for coupling theupper component 304 to the lower component 306.

Consistent with the retrograde access system disclosed herein, theretrograde access path may be oriented at an angle relative to thearticular surface 40 and/or at an angle relative to a normal axisgenerally at the center of the excised region of the articular surface40. As a result, the implant site 78 may generally have a circularcross-section that may be oriented at an angle relative to the articularsurface 40. Consistent with such an embodiment, the angular intersectionof the implant site 78 and the articular surface 40 may provide agenerally oval or elliptical shape of the implant site 78 at thearticular surface 40.

Consistent with the geometry of the implant site 78, the implant 300 maybe generally provided having a cylindrical shape corresponding to theimplant site 78. The shape of the load bearing surface 302 may generallybe defined by the cylindrical geometry of the implant 300 bounded at theload bearing surface by a plane at an angle to the axis of the cylinder.The angle of the plane defining the shape of the load bearing surface302 may generally correspond to the angle of the implant site 78relative to a normal axis through the articular surface 40 at the centerof the implant site 78. Accordingly, the load bearing surface 302 mayhave a generally elliptical or oval shape, as best observed in FIG. 27.

In addition to having an oval or elliptical shape, an implant 300consistent with the foregoing description may have an angled profilealong the longitudinal axis of the implant 300. In the illustratedembodiment, the upper component 304 of the implant is provided having agenerally uniform height. In order to accommodate the geometry of theimplant site 78, the lower component 306 of the implant 300 may beprovided having an angled configuration, relative to the longitudinalaxis thereof.

Turning to FIG. 26, as shown the sides 316 of the lower component mayinclude cutouts 326. The cutouts 326 may reduce the amount of materialof the lower component 306. The reduction in material afforded by thecutouts 326 may provided a corresponding reduction in the weight of thelower component. Additionally, the cutouts 326 may facilitate retentionof the implant 300 in the implant site 78. For example, the cutouts 326may allow the ingrowth of bone and/or mechanical coupling between theimplant 300 and surrounding bone, e.g., using bone cement.

Referring to FIG. 29, another embodiment of a lower component 306 a isillustrated. The lower component 306 a may be formed generally asdescribed with respect to the preceding embodiment, however, the lowercomponent may include a projection 328 extending around at least aportion of the lower component 306. The projection 328 may facilitateanchoring the implant 300 in the implant site 78 formed in the bone 44.When the implant 300 is installed within the implant site 78 theprojection 328 may engage the bone 44 around at least a portion of thecircumference of the implant site 78. The projection 328 may dig intothe bone 44 and resist extraction of the implant 300 from the implantsite 78.

The implant 300 may be installed into the implant site 78 formed in thearticular surface 40 by introducing the implant 300 into the implantsite 78 from the articular surface 40. According to a first method, thelower component 306 may be at least partially inserted into the implantsite 78 separately from the upper component 304. The lower component 306may be introduced into the implant site 78 by urging the lower component306 into the implant site 78 from the articular surface 40 of the bone.Alternatively, or additionally, a tether may be inserted through theretrograde access tunnel 52 and through at least a portion of theimplant site 78. The tether may be coupled to the lower component 306and the lower component 306 may then be pulled into the implant site 78by withdrawing the tether through the access tunnel 52. According toeither embodiment, the lower component 306 may be oriented relative tothe implant site 78 and may be at least partially seated into theimplant site, either from the articular surface 40 or through the accesstunnel 52.

Bone cement and/or mechanical features may be used for securing thelower component 306 in position within the implant site 78. After thelower component 306 has been installed in the implant site 78, the uppercomponent 304 may be installed into the implant site 78 and into thelower component 306. The locking feature 318 of the upper component 304may be oriented and aligned with the locking recess 320 in the lowercomponent 306. The upper component 304 may then be seated in the implantsite 78 with the locking feature 318 of the upper component 304 coupledto the locking recess 320 of the lower component 306. As withinstallation of the lower component 306, the upper component 304 may bepressed or urged into the implant site 78 and/or into engagement withthe lower component 306 by applying a force on the load bearing surface302 of the upper component 304. Alternatively, or additionally, a rigidand/or flexible tether may be coupled to the upper component 304. Theupper component 304 may then be urged into the implant site 78 and/orinto engagement with the lower component 306 by pulling the tetherthrough access tunnel 52 formed in the bone 44.

Consistent with an alternative embodiment, the upper component 304 maybe assembled to the lower component 306 prior to installation of theimplant 300 into the implant site 78. The locking feature 318 of theupper component 304 may be inserted into the locking recess 320 of thelower component 306 to assembly the implant 300. The assembled implant300 may then be installed in the implant site 78. Similar to thepreceding method, the implant 300 may be pressed into the implant site78 by applying a force or impact to the load bearing surface 302 of theimplant. Alternatively, or additionally, a rigid and/or flexible tethermay be coupled to the implant 300. The implant 300 may then be urgedinto the implant site 78 by applying a force on the tether extendingthrough the access tunnel 52 through the bone 44.

According to one aspect, the implant 300 including an assembly of anupper component 304 and a lower component 306 may allow thecharacteristics of the implant 300 to be customized. For example, thelower component 306 may be formed from a material that may providestrength and rigidity to support the upper component 304. Materials wellknown in the field of orthopedics may be used for the lower component306. For example, stainless steel, titanium, cobalt-chromium alloys,etc. may be suitable for producing the lower component 306.

The upper component 304 and/or at least a portion of the upper component304, for example a portion including the load bearing face 302, may beformed from biocompatible material that may provide any variety ofdesirable characteristics. For example, the upper component 304 may beselected to provide a low friction surface or to provide wearresistance. Additionally, the upper component 304 may include a materialselected to provide at least some degree of shock absorption orcushioning effect. Suitable materials may include various polymericmaterials, for example, high density polyethylene, ultrahigh molecularweight polyethylene, polyurethane, polyhydroxy-ethyl methacrylate gel,silicone, polyvinyl alcohol gel, etc. Ceramic materials, such as aluminaor zironia based materials, may also be used, e.g., to provide aninherent lubrication or low friction load bearing surface 302.Additionally, the upper component 304 may include materials that releaseor produce therapeutic or lubricating products and may even includebiological materials. Those having skill in the art will appreciatenumerous other materials that may be used to produce an upper componentaccording to the present disclosure, including various metallic and/orcomposite materials. According to one embodiment, the upper componentmay be formed from a hydrogel material, for example a polyvinyl alcoholhydrogel material.

Consistent with the foregoing, according to one aspect a of the presentdisclosure a method is provided for replacing a portion of an articularsurface. The method may include locating a portion of the articularsurface and creating an access tunnel through bond behind the articularsurface. The tunnel may be provided extending toward the articularsurface. The method may further include installing a guide sheath atleast partially in the access tunnel and excision at least a portion ofthe articular surface.

According to another aspect of the present disclosure, there may beprovided an apparatus for excising a portion of an articular surface.The apparatus may include a drive shaft and a cutter that is capable ofbeing engaged to the drive shaft. The cutter may be moveable between afirst position extending from the drive shaft and a second position notextending from the drive shaft.

According to another aspect of the present disclosure, an implant may beprovided. The implant may include an upper component having a loadbearing surface for replacing a portion of an articular surface. Theload bearing surface may have a geometry based on a geometry of theportion of the articular surface being replace. The upper component mayfurther include an upper locking feature. The implant may also include alower component that may be configured to be at least partially disposedin an implant site formed in the articular surface. The lower componentmay include a recess capable of receiving at least a portion of theupper component. The lower component may also include a lower lockingfeature which may be capable of engaging said locking feature of saidupper component.

Various other features and advantages of the articular replacementsystem described herein will be appreciated by those having skill in theart. Similarly, the system disclosed herein is susceptible to numerousmodifications and variations without materially departing from thespirit of the disclosure.

What is claimed is:
 1. A method of replacing a portion of an articularsurface comprising: locating a portion of said articular surface;creating an access tunnel through bone behind said articular surface,said tunnel extending toward said articular surface; securing at least apart of a guide sheath to, and at least partially within, said accesstunnel and below said articular surface; and excising at least a portionof said articular surface, said excising comprising inserting anexcision tool at least partially through said secured guide sheath.
 2. Amethod according to claim 1, wherein locating a portion of saidarticular surface comprises providing a reference axis extending throughsaid articular surface relative to said portion of said articularsurface.
 3. A method according to claim 2, wherein providing saidreference axis comprises providing a drill guide having a cannulatedshaft comprising a lumen defining an axis extending through saidarticular surface relative to said portion of said articular surface. 4.A method according to claim 3, wherein providing said reference axisfurther comprises inserting a guide pin through said cannulated shaftand into said bone behind said articular surface.
 5. A method accordingto claim 4, wherein creating said access tunnel comprises drilling apassage over said guide pin.
 6. A method according to claim 1, whereinsecuring said guide sheath comprises threadably engaging said guidesheath in said access tunnel.
 7. A method according to claim 1, whereinexcising at least a portion of said articular surface comprisesinserting an excision tool at least partially through said guide sheathand deploying a cutting blade.
 8. A method according to claim 7, furthercomprising rotating said excision tool and translating said excisiontool relative to said articular surface to create an excision site.
 9. Amethod according to claim 1, wherein excising at least a portion of saidarticular surface comprises translating said excision tool relative tosaid articular surface to create an excision site.
 10. A methodaccording to claim 9, wherein said excision site has a cross-sectionthat is larger than a cross-section of said access tunnel.
 11. A methodaccording to claim 9, wherein translating said excision tool relative tosaid articular surface to create said excision site comprisestranslating said excision tool until said excision tool contacts saidguide sheath.
 12. A method according to claim 9, wherein securing saidat least a part of said guide sheath comprises securing said guidesheath to, and at least partially within, said access tunnel apredetermined distance from said articular surface.
 13. A methodaccording to claim 12, wherein said predetermined distance generallycorresponds to a depth of said excision site.
 14. A method according toclaim 9, further comprising inserting an implant at least partiallywithin said excision site.
 15. A method according to claim 9, whereinsaid excision tool comprises: a shaft configured to be received throughsaid guide sheath and to axially rotate therein relative to saidlongitudinal axis of said guide sheath; and at least one cutter coupledto said shaft to axially rotate with said shaft relative to saidlongitudinal axis of said guide sheath to excise said a least a portionof said articular surface in a retrograde manner as said at least onecutter is urged towards a distal end of said guide sheath.
 16. A methodaccording to claim 15, wherein said at least one cutter includes atleast a portion of a cutting surface extending radially outwardly beyondan outer diameter of said guide sheath and a shelf configured to contactagainst said distal end of said guide sheath to control a depth of saidexcision site as said excision tool is urged towards said distal end ofsaid guide sheath in a retrograde manner.
 17. A method according toclaim 1, wherein said guide sheath comprises a generally tubular bodydefining a passageway extending along a longitudinal axis of said guidesheath from a proximal end to a distal end of said guide sheath.
 18. Amethod according to claim 17, wherein at least a portion of an outersurface of said tubular body includes a threaded portion configured toengage with said access tunnel such that said guide sheath is configuredto provide positive alignment with a reference axis of said accesstunnel.
 19. A method according to claim 1, wherein a distal end of saidguide sheath comprises a taper configured to facilitate alignment ofsaid guide sheath with said access tunnel
 20. A method of replacing aportion of an articular surface comprising: locating a portion of saidarticular surface; creating an access tunnel through bone behind saidarticular surface, said tunnel extending toward said articular surface;securing at least a part of a guide sheath to, and at least partiallywithin, said access tunnel and below said articular surface; insertingan excision tool at least partially through said guide sheath; androtating said excision tool and translating said excision tool relativeto said articular surface to create an excision site.